An ink containing water, a water-soluble organic solvent and a colorant, wherein the ink exhibits a (.gamma. cos .theta.).sup.1/2 value of 4 to 6, and satisfies Formula (I): 0.3.ltoreq.((.gamma.' cos .theta.').sup.1/2/(.gamma. cos .theta.).sup.1/2).ltoreq.0.85, wherein .gamma. represents a surface tension (mN/m) of the ink upon initial exposure to atmospheric conditions, .theta. represents an initial contact angle of the ink with respect to plain paper upon initial exposure to atmospheric conditions; and .gamma.' represents a surface tension (mN/m) of the ink after standing for one hour at 40.degree. C. and relative humidity of 2 percent, and .theta.' represents an initial contact angle of the ink with respect to plain paper after standing for one hour at 40.degree. C. and relative humidity of 2 percent.
